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I don't know how to tell myself so need help, please. It does look like there is still metal to be used for braking, but the brakes barely grab these and instead make a squeaking sound.

I have replaced them with new ones and new work great, but I wonder if these just need some help to get working again maybe?enter image description hereenter image description here

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    A @juhist has said there is still plenty of life left in the pads. I would clean them with Isopropyl Alcohol to remove any surface contamination and then when dry, sand them down with a fine sand paper. Then when fitted again follow a proper bedding in process.
    – DWGKNZ
    Oct 14, 2021 at 17:48
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    Question - did you adjust the pads to allow for wear ?
    – Criggie
    Oct 14, 2021 at 18:44
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    These are one of Shimano's models. There would be a visual indicator that appears once the pad is worn out, see here: si.shimano.com/pdfs/si/SI-8J50A-002-ENG.pdf
    – Weiwen Ng
    Oct 14, 2021 at 19:31
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    @Criggie these are hydraulic so they autoadjust
    – Ivan
    Oct 14, 2021 at 19:33
  • N04C are metallic, so take a blowtorch to those pads until you smoke all the oil out. You can heat them to straw-colored (~200C) no problem. They are bloody expensive to be replacing so whimsically.
    – MaplePanda
    Oct 15, 2021 at 3:51

2 Answers 2

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Manufacturers usually prescribe the maximum allowable wear, resp. the minimum allowable thickness, of the pad. That includes some safety margin and you can indeed go much farther, but at your own risk.

One of the pages that summarize these limits is https://bikeco.com/mtb-brake-pad-wear-limits/ Shimano allows to go to 0.5 mm of the pad thickness. Again, some people will go to almost 0, but at their own risk.

You also have to consider that the wear is often uneven. The minimal thickness should be kept across the whole surface.

You can use a dedicated brake cleaner or isopropyl alcohol or denaturated alcohol to clean them. Some will use a blowtorch or gas stove, I would first just try to burn off the alcohol put on the pad by a lighter.

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There's still plenty of life in them.

Pads are worn when there's so little material that the pad spreading spring can start to touch the brake rotor.

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